Pulping of empty fruit bunches (EFB) from the palm oil industry by formic acid

Abstract

Empty fruit bunches (EFB) from palm oil were characterized. The holocellulose (66.97%), α-cellulose (47.91%), and lignin (24.45%) are similar to wood materials, and various non-wood materials, but the fiber length is shorter (0.53 mm). The influence of operational variables in the EFB pulping [formic acid (75-95%), hydrochloric acid (0.05-0.15%), and time (30-150 min)], on the yield, kappa number, viscosity, and brightness of the pulps was studied. By using a factorial design, equations that reproduced the experimental results for the dependent variables, errors less than 10% were obtained. These equations could be used to find suitable conditions, so that operating with not too high values of operating variables (with minor costs of capital and of operation), pulps could be obtained with acceptable properties. In this way, a cellulosic pulp with a 42.3% yield, 22.7% brightness, and a 512 mL/g viscosity was obtained under the following conditions: 92.5% of formic acid, 0.075% of hydrochloric acid, and a time of 60 min. A pulp (31.1 kappa number and 606 mL/g viscosity) was bleached by EPabOPoP sequence, achieving a brightness of 69.4%, a loss of viscosity and yield of 34.8% and 13.1%, respectively. The residual liquor from the pulping with formic acid 95%, 0.05% hydrochloric acid and 30 min, provides a liquor with 18.2% residual lignin, 4.1% glucose, 9.8% xylose, and 1.2% arabinose, all on dry weight of original material.